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Vitamin B-3

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Niacin (Vitamin B-3) is a water-soluble vitamin required by all living cells. It functions in the release of energy from carbohydrates, fats, and proteins. Niacin is also involved in the synthesis of protein, fat, and pentoses needed for nucleic acid formation.

Niacin is a major constituent of the coenzyme nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). These compounds function to remove hydrogen atoms during biological reactions.


Niacin is absorbed in the intestine; little is stored in the body and any excess of the vitamin is excreted in the urine.

Niacin functions as a component of the coenzymes nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). These enzymes are involved in respiration where they act as hydrogen acceptors. They are essential in the reactions involved in the release of energy from carbohydrates, fats, and proteins.

Niacin can be synthesized in the body from tryptophan. Only the L-isomer of tryptophan can be converted into niacin, and the conversion requires the presence of thiamine, pyridoxine, and riboflavin.

Niacin is stable to heat, light, acid and alkali; therefore, little is lost during processing. Vitamin B-Complex, vitamin B-1, Vitamin B-2, Vitamin C, and phosphorus assist the absorption of niacin. Alcohol, coffee, corn, sugar, starches, and excess carbohydrates prevent absorption.


The major clinical application of niacin is in the treatment of pellagra.

There is also evidence which suggest that doses of one to two grams of niacin three times per day may result in lowered blood cholesterol levels. This may protect against recurrent nonfatal heart attacks.

Large doses of niacin have also been used to treat schizophrenia. Orthomolecular therapy, using extremely large amounts of vitamins, is a controversial treatment of psychiatric problems, as critics say that not enough scientific evidence exists to support the claims made. Since the ingestion of large therapeutic amounts of nicotinic acid usually produces a flushing reaction, niacin prescribed for nutritional deficiency is frequently taken as nicotinamide, though the benefits and reactions are not identical to the nicotinic acid form of niacin.

Niacin deficiency is also common in alcoholics. Low levels of niacin are also seen in patients with chronic hepatic failure.


There are many symptoms of niacin deficiency. Initially, muscular weakness, anorexia, indigestion, and skin eruptions occur, with severe deficiencies of niacin commonly leading to pellagra. Symptoms of pellagra include dermatitis, senile dementia, and diarrhea. Tremors and a sore tongue are also symptomatic. With pellagra, the skin becomes cracked and pigmented in the parts exposed to sunlight. Lesions can appear in the central nervous system, producing confusion, disorientation and neuritis. Inflammation of the mucous membranes of the mouth and the gastrointestinal tract can result from digestive abnormalities developed in niacin deficiency. Symptoms of severe riboflavin deficiency appear; many of the niacin deficiencies are similar due to the close interrelationship of riboflavin and niacin in cell metabolism.

Often, people who suffer from pellagra are on very inadequate diets in which corn is a main foodstuff. Such a diet contains little niacin, while the tryptophan in the corn is unavailable and cannot be absorbed from the intestine. Thus, there is no tryptophan available for conversion to niacin and niacin deciency results.

Presoaking corn in lye makes tryptophan available for absorption, due to the presence of alkali.


No real toxic effects of niacin are known. However, large doses cause side effects such as: a tingling sensation, flushing of the skin, gastrointestinal distress, unusual nervousness, and glucose intolerance.


Niacin requirements are affected by such factors as: aging, growth periods, body size, physical activity, illness, tissue trauma, pregnancy and lactation. The RDA standard, 6.6 mg per 1,000 kilocalories (but not less than 13 niacin equivalents at intakes of less than 2,000 kilocalories), is about 50% higher than the minimum requirement; this is in order to provide a safety margin to cover variances in individual need. These recommendations also allow for the contribution of tryptophan, in terms of niacin equivalents, from dietary protein sources. The daily allowance of vitamin B-3 should be based on caloric intake.

RDA for men - 19 mg

RDA for women - 15 mg

RDA for children 7 to Years - 13 mg

RDA for infants - 6 mg

RDA for pregnant and lactating women - 20 mg

Note: It is recognized that one milligram of niacin is derived from each 60 mg of dietary tryptophan.

Food Sources

· Organ Meats

· Halibut

· Rice Bran

· Tuna

· Brewer's Yeast

· Roasted Peanuts

· Swordfish

· Nuts

· Brown Rice

· Corn

· Broccoli

· Avocados

· Dates

· Figs

· Green Peas

· Lima Beans

· Mushrooms

· Wheat/Wheat Germ

· Potatoes

· Parsley

· Swiss Cheese


· Pellagra

· Dermatitis, Diarrhea, and Dementia

· Muscular Weakness

· General Fatigue

· Anorexia

· Indigestion

· Insomnia

· Irritability

· Stress

· Depression

· Schizophrenia

· Excessive Blood Cholesterol

· Poor Learning Ability

· Arthritis and Joint Malfunctions

· Gastrointestinal Upsets Such As:

· Nausea

· Vomiting

· Inflammation of Mouth and Digestive Track

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